A Classroom Soundfield System is essentially a small public address sound system, designed for the confines of a typical classroom of 25 – 35 students.
From a hardware standpoint, the system usually consists of two wireless microphones. One is primarily for the teacher, and the second microphone is generally used by students. Most sound-field systems are currently using infrared wireless microphone technology. Since infrared is based on pulsating light, the transmission of the wireless microphones will not penetrate the walls of a classroom into another room. This allows us to set up dozens or even hundreds of classrooms very close to each other with no interference.
The system also features a built in mixer and amplifier that will also be able to amplify audio from such sources as a computer, a DVD, TV tuner, or even an Ipod.
The next critical part of a Sound-field System consists of several (four or more) overhead ceiling speakers. The key to really making a Sound-field system work effectively is a smooth “wash” of sound throughout the entire classroom. Ideally, every student should be listening at a distance of about six feet from the nearest loudspeaker so that we maintain the illusion of having the teacher standing six feet in front of you.
Ceiling loudspeakers are kind of like ceiling light bulbs. For even coverage, you wouldn’t use just one or two to cover the entire classroom. The same goes for ceiling loudspeakers.
The main problem that students encounter while trying to listen to instruction is that they are simply too far from the teacher’s voice and the classroom can be a noisy environment with computers and air conditioning.
In a world of Ipods, loud car stereos, very loud movie theatres, noisy video games and home television, most students simply do not pay attention to low sound levels (or teacher’s instructions) that are less than 63-65 decibels.
If a teacher tries to produce 75 decibels of sound at arm’s length (about 18”) they will find that this is no easy feat. Plus, that 75 decibel sound wave is going to be reduced to 63 decibels at six feet from the teacher’s voice. (that old inverse square law rule from physics class). The front row in most schools is about six feet from the teacher.
Back to that 63 decibel level at the first row……….Once you move back a couple of rows to twelve feet from the teacher, the teacher’s voice drops another 6 decibels to about 57 decibels. The very last row tends to be about 20 – 24 feet from the teacher’s voice and although inverse square law tends to stop being a factor after about 18 ft, that distance produces another 2-3 decibels in loss of sound. That final sound level from the teacher at 54 – 55 decibels in the back rows is simply not enough to get good student attention. Thus, the need for amplification.
Plus, if the teacher turns his/her back to the students while at the chalkboard/interactive board, the teacher’s voice is “splattered” and reflected off the front wall or screen and is much more difficult for any students to understand.
In summary, wearing a wireless microphone allows the teacher’s voice to always appear as if he/she is facing the student and the amplified overhead ceiling speakers give the illusion of the teacher only being six feet away. The magic of modern technology.